Relief valves are used to control or limit the pressure in a system or vessel which can build up by a process upset or fire in the vessel. In particular, relief valves are used on vessels such as tank cars carrying commodities like ethanol or crude oil to allow the pressurized contents to flow from the relief valve in the event of a fire or other system failure. Present relief valves used with railroad tank cars open when the pressure in the vessel rises above a predetermined amount, but such valves do not remain open after the initial quick release in pressure. In these valves, the poppet of the valve re-seats when the initial quick release in pressure is achieved, thus not allowing additional pressure or contents to be relieved from the vessel. The present relief valve solves the existing limitations.